It is known in the automotive industry to include an exhaust gas treatment system utilizing gasoline particulate filters or diesel particulate filters and/or one or more catalytic units, such as a catalytic converter, diesel oxidation catalyst unit, or selective catalytic reduction catalyst unit to improve the emissions in the exhaust. In such catalytic units, it is common for a catalyst to be carried as a coating on a supporting substrate structure, such as a ceramic substrate having a monolithic structure, and in particulate filters it is common to employ a monolithic filter structure that can be non-catalytic.
Typically, such monolithic structures are oval or circular in cross section and are often wrapped with a layer of a support or mounting mat that is positioned between the monolithic structure and the outer housing of the unit to help protect the monolithic structure from shock and vibrational forces that can be transmitted from the housing to the monolithic structure. In addition, material to insulate and reduce the heat loss from the monolithic structure has been included with the support mat. One such structure is shown and described in U.S. Publication No. 2010-023946A1 which is hereby incorporated by reference. Typically, the support or mounting mat is made of a heat resistant and shock absorbing type material, such as a mat of glass fibers, ceramic fibers, or rock wool.
Manufacture of such structures can be difficult and costly. Further, such structures can break down and fail to provide the functional characteristics and properties desired before the useful life of, for example, the vehicle, is over. It is therefore advantageous to provide such monolithic structures which maximize their useful life.